"It means their detention network can't hold them [and] they can't send them to Nauru because their deterrence policies are non-existent."

Meanwhile, the government has expelled another 46 asylum seekers from Sri Lanka, all recent arrivals from a number of boats.

While advocates and asylum seekers accused the government of sending people home without properly investigating their claims for asylum, Immigration Minister Chris Bowen said: "The government will continue to return people where they do not engage Australia's international [protection] obligations."

Earlier, he told ABC Radio that many of the Sri Lankans forcibly returned to their home were economic migrants. "This is a very appropriate process," Mr Bowen said.

"It's a process which does make sure that where people come to Australia for economic purposes, which is being sold by people smugglers – 'You can go to Australia; even if you are eventually returned after several years you'll be able to work' – this is one of the mechanisms we are using to deal with that."